fix cli empty-long arg panic and optional --db in memory mode

CHANGELOG.md

@@ -4,6 +4,13 @@ All notable changes to this project will be documented in this file.
 
 Each entry lists the date and the crate versions that were released.
 
+## 2026-05-28 — mqdb-cli 0.8.6
+
+### Fixed
+
+- `mqdb agent start` (and `cluster start`) panicked at startup on every invocation in debug builds: `thread 'main' panicked ... Long option names must be unique ... '--' is in use by both 'passwd_data' and 'acl_data'`. Seventeen optional inline-content args (`passwd_data`, `acl_data`, `scram_data`, the `*_data`/`*_key`/`*_secret` variants in both agent and cluster) were declared `#[arg(long = "")]`, which clap registers as the empty long option `--`; the duplicates tripped clap's `debug_assert`, crashing every debug-build command before parsing (release builds skip the assert, so the flags were silently mis-defined and never parsed). Each now has a distinct hidden long name (`--passwd-data`, `--acl-data`, `--scram-data`, …), so debug builds run and the inline-content flags parse correctly while staying hidden from `--help`. Added a `Cli::command().debug_assert()` regression test so a future empty/duplicate long name fails CI instead of only crashing debug binaries.
+- `mqdb agent start --memory-backend` no longer requires `--db`. The flag is now `required_unless_present = "memory_backend"`; in memory mode without a path it defaults to a temp directory, which the in-memory backend never touches. Callers no longer need to pass a dummy `--db`.
+
 ## 2026-05-28 — mqdb-core 0.7.1, mqdb-agent 0.8.5, mqdb-vault 0.1.1, mqdb-wasm 0.3.3, mqdb-cli 0.8.5
 
 ### Added

crates/mqdb-cli/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mqdb-cli"
-version = "0.8.5"
+version = "0.8.6"
 publish = false
 edition.workspace = true
 license = "AGPL-3.0-only"

crates/mqdb-cli/src/cli_types/agent.rs

@@ -17,8 +17,13 @@ pub(crate) struct AgentStartFields {
         help = "Address to bind MQTT listener"
     )]
     pub(crate) bind: SocketAddr,
-    #[arg(long, env = "MQDB_DB", help = "Path to database directory")]
-    pub(crate) db: PathBuf,
+    #[arg(
+        long,
+        env = "MQDB_DB",
+        required_unless_present = "memory_backend",
+        help = "Path to database directory (optional with --memory-backend)"
+    )]
+    pub(crate) db: Option<PathBuf>,
     #[arg(
         long,
         env = "MQDB_MEMORY_BACKEND",
@@ -79,15 +84,15 @@ pub(crate) struct AgentStartFields {
         help = "Path to file containing encryption passphrase"
     )]
     pub(crate) passphrase_file: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_PASSPHRASE", hide = true)]
+    #[arg(long = "passphrase-data", env = "MQDB_PASSPHRASE", hide = true)]
     pub(crate) passphrase_data: Option<String>,
     #[arg(long, env = "MQDB_LICENSE_FILE", help = "Path to license key file")]
     pub(crate) license: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_LICENSE", hide = true)]
+    #[arg(long = "license-data", env = "MQDB_LICENSE", hide = true)]
     pub(crate) license_data: Option<String>,
-    #[arg(long = "", env = "MQDB_QUIC_CERT", hide = true)]
+    #[arg(long = "quic-cert-data", env = "MQDB_QUIC_CERT", hide = true)]
     pub(crate) quic_cert_data: Option<String>,
-    #[arg(long = "", env = "MQDB_QUIC_KEY", hide = true)]
+    #[arg(long = "quic-key-data", env = "MQDB_QUIC_KEY", hide = true)]
     pub(crate) quic_key_data: Option<String>,
     #[arg(
         long,
@@ -240,17 +245,17 @@ pub(crate) struct ClusterStartFields {
         help = "Path to file containing encryption passphrase"
     )]
     pub(crate) passphrase_file: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_PASSPHRASE", hide = true)]
+    #[arg(long = "passphrase-data", env = "MQDB_PASSPHRASE", hide = true)]
     pub(crate) passphrase_data: Option<String>,
     #[arg(long, env = "MQDB_LICENSE_FILE", help = "Path to license key file")]
     pub(crate) license: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_LICENSE", hide = true)]
+    #[arg(long = "license-data", env = "MQDB_LICENSE", hide = true)]
     pub(crate) license_data: Option<String>,
-    #[arg(long = "", env = "MQDB_QUIC_CERT", hide = true)]
+    #[arg(long = "quic-cert-data", env = "MQDB_QUIC_CERT", hide = true)]
     pub(crate) quic_cert_data: Option<String>,
-    #[arg(long = "", env = "MQDB_QUIC_KEY", hide = true)]
+    #[arg(long = "quic-key-data", env = "MQDB_QUIC_KEY", hide = true)]
     pub(crate) quic_key_data: Option<String>,
-    #[arg(long = "", env = "MQDB_QUIC_CA", hide = true)]
+    #[arg(long = "quic-ca-data", env = "MQDB_QUIC_CA", hide = true)]
     pub(crate) quic_ca_data: Option<String>,
 }
 

crates/mqdb-cli/src/cli_types/auth.rs

@@ -11,11 +11,11 @@ use super::base::JwtAlgorithmArg;
 pub(crate) struct AuthArgs {
     #[arg(long, env = "MQDB_PASSWD_FILE", help = "Path to password file")]
     pub(crate) passwd: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_PASSWD", hide = true)]
+    #[arg(long = "passwd-data", env = "MQDB_PASSWD", hide = true)]
     pub(crate) passwd_data: Option<String>,
     #[arg(long, env = "MQDB_ACL_FILE", help = "Path to ACL file")]
     pub(crate) acl: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_ACL", hide = true)]
+    #[arg(long = "acl-data", env = "MQDB_ACL", hide = true)]
     pub(crate) acl_data: Option<String>,
     #[cfg(feature = "dev-insecure")]
     #[arg(long, help = "Allow anonymous connections (dev only)")]
@@ -26,7 +26,7 @@ pub(crate) struct AuthArgs {
         help = "Path to SCRAM-SHA-256 credentials file"
     )]
     pub(crate) scram_file: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_SCRAM", hide = true)]
+    #[arg(long = "scram-data", env = "MQDB_SCRAM", hide = true)]
     pub(crate) scram_data: Option<String>,
     #[arg(
         long,
@@ -41,7 +41,7 @@ pub(crate) struct AuthArgs {
         help = "Path to JWT secret/key file"
     )]
     pub(crate) jwt_key: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_JWT_KEY", hide = true)]
+    #[arg(long = "jwt-key-data", env = "MQDB_JWT_KEY", hide = true)]
     pub(crate) jwt_key_data: Option<String>,
     #[arg(long, env = "MQDB_JWT_ISSUER", help = "JWT issuer claim")]
     pub(crate) jwt_issuer: Option<String>,
@@ -56,15 +56,19 @@ pub(crate) struct AuthArgs {
     pub(crate) jwt_clock_skew: u64,
     #[arg(long, env = "MQDB_FEDERATED_JWT_CONFIG_FILE", conflicts_with_all = ["jwt_algorithm"], help = "Path to federated JWT config JSON")]
     pub(crate) federated_jwt_config: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_FEDERATED_JWT_CONFIG", hide = true)]
+    #[arg(
+        long = "federated-jwt-config-data",
+        env = "MQDB_FEDERATED_JWT_CONFIG",
+        hide = true
+    )]
     pub(crate) federated_jwt_config_data: Option<String>,
     #[arg(
         long,
         env = "MQDB_CERT_AUTH_FILE",
         help = "Path to certificate auth file"
     )]
     pub(crate) cert_auth_file: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_CERT_AUTH", hide = true)]
+    #[arg(long = "cert-auth-data", env = "MQDB_CERT_AUTH", hide = true)]
     pub(crate) cert_auth_data: Option<String>,
     #[arg(
         long,
@@ -116,7 +120,11 @@ pub(crate) struct OAuthArgs {
         help = "Path to file containing Google OAuth client secret"
     )]
     pub(crate) oauth_client_secret: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_OAUTH_CLIENT_SECRET", hide = true)]
+    #[arg(
+        long = "oauth-client-secret-data",
+        env = "MQDB_OAUTH_CLIENT_SECRET",
+        hide = true
+    )]
     pub(crate) oauth_client_secret_data: Option<String>,
     #[arg(
         long,
@@ -168,7 +176,7 @@ pub(crate) struct OAuthArgs {
         help = "Path to 32-byte identity encryption key file (auto-generated if omitted)"
     )]
     pub(crate) identity_key_file: Option<PathBuf>,
-    #[arg(long = "", env = "MQDB_IDENTITY_KEY", hide = true)]
+    #[arg(long = "identity-key-data", env = "MQDB_IDENTITY_KEY", hide = true)]
     pub(crate) identity_key_data: Option<String>,
     #[arg(
         long,

crates/mqdb-cli/src/main.rs

@@ -185,7 +185,9 @@ async fn dispatch_agent(action: AgentAction) -> Result<(), Box<dyn std::error::E
         AgentAction::Start(fields) => {
             cmd_agent_start(AgentStartArgs {
                 bind: fields.bind,
-                db_path: fields.db,
+                db_path: fields
+                    .db
+                    .unwrap_or_else(|| std::env::temp_dir().join("mqdb-memory")),
                 memory_backend: fields.memory_backend,
                 auth: *fields.auth,
                 durability: fields.durability,
@@ -557,3 +559,24 @@ async fn dispatch_bench(action: BenchAction) -> Result<(), Box<dyn std::error::E
         }
     }
 }
+
+#[cfg(test)]
+mod cli_tests {
+    use crate::cli_types::Cli;
+    use clap::{CommandFactory, Parser};
+
+    #[test]
+    fn cli_definition_is_valid() {
+        Cli::command().debug_assert();
+    }
+
+    #[test]
+    fn memory_backend_makes_db_optional() {
+        let parsed = Cli::try_parse_from(["mqdb", "agent", "start", "--memory-backend"]);
+        assert!(
+            parsed.is_ok(),
+            "--memory-backend should not require --db: {:?}",
+            parsed.err()
+        );
+    }
+}